The present invention relates to detection of contrast injection in fluoroscopic image sequences, and more particularly to detection of where and when a contrast agent is injected in a fluoroscopic image sequence.
Coronary angiography is a procedure that is recommended preoperatively for patients who are suffering from or at risk for coronary artery disease. Angiography is a medical imaging technique in which X-ray images are used to visualize internal blood filled structures, such as arteries, veins, and the heart chambers. Since blood has the same radiodensity as the surrounding tissues, these blood filled structures cannot be differentiated from the surrounding tissue using conventional radiology. In angiography, a catheter is inserted into a blood vessel, typically in the groin or the arm. The catheter is guided and positioned either in the heart or in arteries near the heart, and a contrast agent is added to the blood via the catheter to make the blood vessels in the heart visible via X-ray. As the contrast agent travels down the branches of the coronary artery, the vessel branches become visible in the X-ray (fluoroscopic) image. The X-ray images are taken over a period of time, which results in a sequence of fluoroscopic images.
The moment when the contrast is injected provides important temporal information for the automatic analysis of vessels. This temporal information can be used to trigger the starting of automatic vessel detection. For example, this temporal information can be used in implementing Digital Subtraction Angiography (DSA), which detects vessels by subtracting a pre-contrast image or “mask image” from later fluoroscopic images once the contrast agent has been introduced. Furthermore, the spatial location of the contrast injection point can be used as a starting point for vessel detection and tracking. Accordingly, it is desirable to detect the time and location of a contrast injection in a fluoroscopic image sequence.